Plus42 Equations, Preview Release

[Thomas Okken]

New update:

1. Somewhat smarter PLOT axis label placement.
2. Removed the top-level GRAPH menu; GRAPH now takes you directly to the plot settings menu. I'll restore the top-level menu once I get around to actually implementing 3D and other plot types, and for now, focus on improving the 2D plot functionality and getting it ready for 1.0.
3. PRINT in the plot viewer now prints the program name or equation above the plot.
4. Fixed PRGM-mode behavior of the GRAPH menus and functions.